1. Field of the Invention
The present invention relates to a transfer-molding type power semiconductor device and a manufacturing method for the same, and more particularly, to a power semiconductor device in which metal socket electrode terminals for top-exposed electrodes are arranged perpendicularly to an insulating substrate and a manufacturing method for the same.
2. Description of the Background Art
In many cases, typical semiconductor packages are formed by resin sealing including transfer-molding in terms of manufacturing cost, productivity or the like. In the transfer molding, a resin composition (molding resin) is melted by high-frequency heating as required, and then is filled into a hollow (cavity) inside a metal mold kept at high temperature. The metal mold is typically composed of an upper mold and a lower mold combined therewith, and the cavity is defined by inner walls of the upper and lower molds. A plunger is used for filling of the molding resin and the following pressurization of the molding resin, where the molding resin is heat-melted to be filled in the cavity and then is cured. The molding resin is filled in the cavity in a state where mold clamping is performed, and then a semiconductor device which is resin-sealed with a molding resin is manufactured by a known method.
In transfer molding, a metal electrode terminal such as a lead frame is sandwiched in the state of being in contact with the upper and lower molds during mold clamping, and accordingly the metal electrode terminal is exposed to an outside of the resin even after the resin is sealed. The metal electrode terminal described herein is exposed to an outside of the package after the transfer molding to be electrically connected with the outside of the package. In a case where a lead frame is used as the metal electrode terminal, the terminal is typically formed as an external terminal on a periphery of side surfaces of the package molded with a molding resin. However, considering that a plurality of packages are mounted on a printed wiring board at high density to miniaturize a system and a semiconductor device, the metal electrode terminal is desirably exposed to upper surfaces (in a direction perpendicular to a surface of an insulating substrate) of the packages, not to the side surfaces (in a direction parallel to the surface of the insulating substrate) of the packages.
Japanese Patent Application Laid-Open No. 08-204064 discloses a configuration in which metal electrode terminals are exposed in a side surface direction of a package, and Japanese Patent Application Laid-Open No. 2007-184315 discloses a configuration in which metal electrode terminals are exposed in an upper surface direction of a package.
In a transfer-molding type power semiconductor device, electrode terminals are mounted perpendicularly to the insulating substrate in a case where the electrode terminals are exposed to the upper surface of the molding resin (in a direction perpendicular to the surface of the insulating substrate). One end of the electrode terminal is bonded to a circuit pattern and an electrode of a semiconductor element, while the other end thereof needs to be exposed to an outside of the molding resin. Therefore, in mold clamping of the semiconductor device with the upper and lower molds, an end of the metal electrode terminal, which is not bonded to the insulating substrate, needs to be in contact with an inner wall of the mold.
However, if a total thickness from the insulating substrate to a tip of the metal electrode terminal is larger than a length of an inside of a cavity in a longitudinal direction, unfortunately, internal components are damaged by mold clamping. On the other hand, if the total thickness is smaller than the length of the inside of the cavity in the longitudinal direction, the other end of the metal terminal electrode is not brought into contact with the inner wall of the mold in mold clamping. As a result, the metal electrode terminal is not exposed to the outside of the molding resin after injection of the molding resin, which makes it unable to connect an external terminal.
In order to avoid such problems, it is required to strictly control accuracy of dimension of internal components such as an insulating substrate, a power semiconductor, a metal electrode terminal, solder, and a mold, which causes an increase in manufacturing cost or a decrease in yield.
In the case where the metal electrode terminals are formed so as to be exposed from a top of the molding resin, the electrodes can be arranged in proximity to each other on the same surface compared with the case where the metal electrode terminals are exposed from a side surface of the molding resin. Accordingly, the electrodes can be arranged in high density, which is advantageous to miniaturization of a power semiconductor device. Nevertheless, creeping discharge occurs if a creeping distance between the metal electrode terminals is excessively small, and hence the creeping distance imposes a limitation on further miniaturization.